/* eslint-disable */
// 当ctx传入当前文件，const grd = ctx.createCircularGradient() 和
// const grd = this.ctx.createLinearGradient() 无效，因此只能分开处理
// 先分析，在外部创建grd，再传入使用就可以
const api = {
  isGradient(bg) {
    if (bg && (bg.startsWith('linear') || bg.startsWith('radial'))) {
      return true;
    }
    return false;
  },

  doGradient(bg, width, height, ctx)  {
    if (bg.startsWith('linear')) {
      linearEffect(width, height, bg, ctx);
    } else if (bg.startsWith('radial')) {
      radialEffect(width, height, bg, ctx);
    }
  }
}

function analizeGrad(string) {
  const colorPercents = string.substring(0, string.length - 1).split("%,");
  const colors = [];
  const percents = [];
  for (let colorPercent of colorPercents) {
    colors.push(colorPercent.substring(0, colorPercent.lastIndexOf(" ")).trim());
    percents.push(colorPercent.substring(colorPercent.lastIndexOf(" "), colorPercent.length) / 100);
  }
  return {colors: colors, percents: percents};
}

function radialEffect(width, height, bg, ctx) {
  const colorPer = analizeGrad(bg.match(/radial-gradient\((.+)\)/)[1]);
  const grd = ctx.createCircularGradient(0, 0, width < height ? height / 2 : width / 2);
  for (let i = 0; i < colorPer.colors.length; i++) {
    grd.addColorStop(colorPer.percents[i], colorPer.colors[i]);
  }
  ctx.setFillStyle(grd);
  ctx.fillRect(-(width / 2), -(height / 2), width, height);
}

function analizeLinear(bg, width, height) {
  const direction = bg.match(/([-]?\d{1,3})deg/);
  const dir = direction && direction[1] ? parseFloat(direction[1]) : 0;
  let coordinate;
  switch (dir) {
    case 0: console.log('case 0:'); coordinate = [0, -height / 2, 0, height / 2]; break;
    case 90: console.log('case 90:'); coordinate = [width / 2, 0, -width / 2, 0]; break;
    case -90: console.log('case -90:'); coordinate = [-width / 2, 0, width / 2, 0]; break;
    case 180: console.log('case 180:'); coordinate = [0, height / 2, 0, -height / 2]; break;
    case -180: console.log('case -180:'); coordinate = [0, -height / 2, 0, height / 2]; break;
    default:
      let x1 = 0;
      let y1 = 0;
      let x2 = 0;
      let y2 = 0;
      if (direction[1] > 0 && direction[1] < 90) {
        x1 = (width / 2) - ((width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
        y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
        x2 = -x1;
        y1 = -y2;
      } else if (direction[1] > -180 && direction[1] < -90) {
        x1 = -(width / 2) + ((width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
        y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
        x2 = -x1;
        y1 = -y2;
      } else if (direction[1] > 90 && direction[1] < 180) {
        x1 = (width / 2) + (-(width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
        y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
        x2 = -x1;
        y1 = -y2;
      } else {
        x1 = -(width / 2) - (-(width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
        y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
        x2 = -x1;
        y1 = -y2;
      }
      coordinate = [x1, y1, x2, y2];
      break;
  }
  return coordinate;
}

function linearEffect(width, height, bg, ctx) {
  const param = analizeLinear(bg, width, height);
  const grd = ctx.createLinearGradient(param[0], param[1], param[2], param[3]);
  const content = bg.match(/linear-gradient\((.+)\)/)[1];
  const colorPer = analizeGrad(content.substring(content.indexOf(',') + 1));
  for (let i = 0; i < colorPer.colors.length; i++) {
    grd.addColorStop(colorPer.percents[i], colorPer.colors[i]);
  }
  ctx.setFillStyle(grd);
  ctx.fillRect(-(width / 2), -(height / 2), width, height);
}
export default api
